Elevator dispatch algorithm playground

elevator-core is a deterministic, engine-agnostic Rust simulation library for elevators. This in-browser playground lets you compare dispatch strategies side-by-side on identical rider traffic, tweak car count, max speed, capacity, and door cycle, and share a permalink that reproduces the exact run. The same crate runs natively in Bevy, in Unity and GameMaker through a C ABI, in Godot via a gdext extension, and in the browser via wasm-bindgen.

Why elevator-core

• Engine-agnostic core. The simulation library has zero engine dependencies. Every host (Bevy, Unity, Godot, GameMaker, web) wraps the same crate.
• Deterministic, snapshot-replayable. Same config + seed produces bit-identical state tick-for-tick across hosts. Enforced in CI by a cross-process harness.
• Pluggable dispatch. Six built-in strategies plus a DispatchStrategy trait for custom controllers, settable per elevator group.
• Game-agnostic riders. A rider is anything that rides; consumers attach game semantics through extension storage.
• Stops at arbitrary distances. Floors aren't uniformly spaced — the same primitives model a five-floor convention center and a kilometre-tall space elevator.

Dispatch strategies

• SCAN — sweeps end-to-end like a disk head. Simple, predictable, ignores who's waiting longest.
• LOOK — like SCAN but reverses early when nothing is queued further. A practical baseline.
• NEAREST — grabs whichever call is closest right now. Fast under light load, thrashes under rush.
• ETD — estimated time of dispatch. Assigns each call to whichever car can finish fastest.
• DCS — destination-control system. Riders pick their floor at the lobby; the group optimises assignments.
• RSR — relative system response. A wait-aware variant of ETD that penalises long queues.

Idle-parking strategies

• Adaptive — switches based on traffic; returns to lobby during up-peak, predicts hot floors otherwise. Default.
• Predictive — parks idle cars near whichever floor has seen the most recent arrivals.
• Lobby — sends every idle car back to the ground floor to prime the morning rush.
• Spread — keeps idle cars fanned out so any floor has a nearby option.
• Stay — leaves idle cars wherever they finished their last delivery.

Scenarios

• Skyscraper — 40 named floors plus three sub-basements and a sky lobby. Models morning rush, midday meetings, lunch crowd, evening commute, and late-night traffic across low/high banks, an executive line, and a service line.
• Space elevator — kilometres-long tether climbers between Earth station and orbital platforms. Stress-tests dispatch and parking when stops are far apart.
• Airport loop — two counter-rotating loops connect a terminal to six concourses. Fixed-headway dispatch on a one-way loop, with demand shifting from outbound (morning) to inbound (evening).
• Convention center — five named stops (Lobby, Exhibit Hall, Mezzanine, Ballroom, Keynote Hall). Tests burst traffic when a keynote lets out.

Frequently asked questions

What is elevator-core?

An engine-agnostic Rust simulation library for elevators. Models cars, stops, lines, riders, doors, and dispatch in a tick-based loop with a struct-of-arrays world. Same crate powers Bevy, Unity / .NET / GameMaker (via C ABI), Godot (via gdext), and the browser (via wasm-bindgen).

Which engines does it support?

Bevy 0.18 natively, plus Unity, .NET, and GameMaker through elevator-ffi, Godot through a gdext extension, and the browser through elevator-wasm. The core crate has zero engine dependencies.

Which dispatch strategies are built in?

Six: SCAN, LOOK, NEAREST, ETD, DCS, and RSR. All implement the DispatchStrategy trait so you can plug in your own.

Is the simulation deterministic?

Yes. Same config + seed produces bit-identical snapshots across every host. elevator-contract enforces this in CI.

Can I share a specific simulator setup?

Yes. The Share button copies a permalink encoding scenario, dispatch and parking strategies for both panes, the seed, intensity, traffic mode, and any tweaked physics parameters.

What is Quest mode?

A 15-stage curriculum that teaches the elevator-core API one primitive at a time. You write a controller in TypeScript inside an embedded Monaco editor and watch your code drive the cars.

Resources

• Source on GitHub — Cargo workspace with ten crates.
• elevator-core on crates.io — the simulation library crate.
• API documentation on docs.rs — generated from rustdoc.
• elevator-core guide — mdBook chapters covering the simulation loop, custom dispatch, snapshots and determinism, host bindings, and integration galleries for Bevy, Unity, Godot, and GameMaker.
• Dispatch strategies guide — deeper write-up of each built-in algorithm.
• Writing a custom dispatch strategy — how to implement the DispatchStrategy trait.

If you can read this, JavaScript or WebAssembly is disabled in your browser; the interactive playground requires both. The links above let you read the same material as static documentation.